A vehicle such as a hybrid electric vehicle and an electric vehicle widespread recently includes a power supply that supplies power to a motor or the like acting as a power source. The power supply includes an assembled battery that is made by stacking a plurality of storage cells. A voltage output from the power supply is boosted by a booster circuit connected to the power supply via a switch such as a system main relay (SMR), and is supplied to the motor.
Under the configuration, there is a technology for preventing the overcharge of a power supply by using redundant monitoring for monitoring a function of monitoring the overcharge of the power supply on the basis of a charging voltage of a capacitor charged by series connection with the power supply, for example. Moreover, for example, there is a technology for detecting insulation abnormality of a vehicle on the basis of a voltage of a capacitor charged in a state where a power supply, the capacitor, a vehicle insulation resistance, and a vehicle body ground are connected to one another (for example, see Japanese Laid-open Patent Publication No. 2014-020914). Moreover, for example, there is a technology for detecting insulation abnormality of a vehicle and for detecting welding of SMR on the basis of a voltage of a capacitor charged in a state where a power supply, the capacitor, and a booster circuit are connected to one another (for example, see Japanese Laid-open Patent Publications No. 2011-166950 and No. 2012-202723).
However, the conventional technology has a problem that the control processing and the circuit configuration are complicated in that the on/off of a switch of a target for welding detection are alternately controlled and in that a circuit for welding detection different from insulation abnormality detection is provided, for example.